The present invention relates to sodium zirconium carbonate, zirconium phosphate, and zirconium basic carbonate and methods of making these compounds.
Sodium Zirconium Carbonate (SZC) is an amorphorous zirconium polymeric compound with the structural formula as shown:
The granular form of the material can be obtained by the following two methods:    Method A: Reaction of granular zirconium basic sulfate with a saturated soda ash solution followed by washing the product to remove the sulfate.    Method B: Controlled polymeric particle growth reaction of a metastable sodium zirconium carbonate solution formed by mixing a soluble zirconium salt solution with an excessive amount of soda ash solution.
One industrial application of granular SZC is the conversion of the material to zirconium basic carbonate (ZBC) which is a commercial raw material in making other zirconium chemical products. The conversion can be made by titrating the granular SZC to pH 3.5–4.0 with an acid to remove the excessive sodium carbonate. The granular SZC used for making ZBC is usually produced by Method A. Another important application of SZC is the conversion of the material to the granular zirconium chemical ion exchangers, namely, zirconium phosphate (ZrP) and hydrous zirconium oxide (HZO). These zirconium ion exchange material are used commercially for renal dialysis application. The quality and economic criteria, which dictate the method of their manufacture, constitute the art of making the REDY® sorbent cartridge for hemodialysate regeneration currently used by SORB™ Technology, Inc., Oklahoma City, Okla. A recent study on the design of a sorbent cartridge at SORB™ Technology, Inc. for peritoneal dialysis (PD) fluid regeneration indicates that the granular SZC by itself has unique properties which make it more beneficial than HZO in contributing to the potency of the sorbent PD cartridge. These properties of the material which make the cartridge adaptable to the PD treatment conditions may be summarized as follows:
1. The material has sufficient phosphate adsorption capacity to remove phosphate from the patient fluid for the treatment of hyperphosphatemia in renal disease patients.
2. The material supplements bicarbonate to the PD fluid, which can be essential to correct metabolic acidosis in patients.
3. The material prevents the pH of PD fluid from falling, which may cause depletion of bicarbonate from the patient. This allows regenerative PD to be feasible.
In order to manufacture the granular SZC for sorbent PD applications, both quality and economic factors have to be considered. Method A cannot be used because the product has high sulfate content that degrades the quality of the material as a sorbent. Method B has been used in production through the use of acid zirconium sulfate tetrahydrate (AZST) as the zirconium raw material. The process efficiency is less and the manufacture cost is higher for this process, but the ZrP made from granular SZC has higher ammonium adsorption capacity than that made from zirconium basic sulfate (ZBS).
While these processes are useful, there is a need to provide a better quality sodium zirconium carbonate and zirconium basic carbonate with uses especially in the dialysis area and further there is a need to reduce the cost of manufacturing these components.